Exhaust emission control

ABSTRACT

Internal combustion engine exhaust gases, passing unreacted through an exhaust gas catalytic or thermal reaction device during the warmup period of the device, are directed to an expansible container which retains the entire flow of exhaust gases or to a container of filter, adsorptive and absorptive material which retains undesirable constituents of the exhaust gases. After warmup of the reaction device, the retained gases or constituents are recirculated to the engine induction system or the reaction device. This approach supplements the emission control of the reaction device by preventing emission of undesirable exhaust gas constituents during starting of the engine and warmup of the reaction device.

Templin et a1.

[ 1 Feb. 29, 1972 EXHAUST EMISSION CONTROL inventors: Robert J. Templin,Bloomfield; Paul R. Johnson, Metamora; Robert F. Falberg, Birmingham,all of Mich.

General -Motors Corporation, Detroit, Mich.

Filed: Sept. 28, 1970 Appl. No.: 75,834

Assignee:

US. Cl ..60/30 R, 123/119 A, 23/2 E, 23/288 F Int. Cl ..F0ln 3/14 Fieldof Search ..60/29 A, 30 R; 123/119 A; 23/288 F, 2 E

References Cited UNITED STATES PATENTS Bilsky ..60/29 A Elliott ..60/30R 3,172,251 3/1965 Johnson ..60/30 R 3,306,033 2/1967 Cornelius... 60/30R 3,393,668 7/1968 Milgram ..60/30 R 3,476,524 11/1969 Burke ..l23/l 19A Primary ExaminerDouglas Hart AttorneyJ. L. Carpenter and C. K.Veenstra [57] ABSTRACT lntemal combustion engine exhaust gases, passingunreacted through an exhaust gas catalytic or thermal reaction deviceduring the warmup period of the device, are directed to an expansiblecontainer which retains the entire flow of exhaust gases or to acontainer of filter, adsorptive and absorptive material which retainsundesirable constituents of the exhaust gases. After wannup of thereaction device, the retained gases or constituents are recirculated tothe engine induction system or the reaction device. This approachsupplements the emission control of the reaction device by preventingemission of undesirable exhaust gas constituents during starting of theengine and warmup of the reaction device.

14 Claims, 9 Drawing Figures Patented Feb. 29, 1972 2 Sheets-Sheet 1VE/V TOPS EXHAUST EMISSION CONTROL BACKGROUND OF THE INVENTION Extensivedevelopment over the past several years indicates that exhaust gasreaction devices, such as catalytic converters and thermal reactorexhaust manifolds, have potential for reacting substantially all theundesirable constituents in internal-combustion engine exhaust gases.However, such devices are relatively inefficient at ambienttemperatures, and the thermal mass of the reaction devices cannot bewarmed to an efficient reaction temperature instantaneously. A period ofabout I to 3 minutes is usually required for the exhaust gases to heat areaction device to its efficient reaction temperature. Thus exhaustgases formed during starting of the engine and during this warmup periodare incompletely reacted. It is believed that a very high proportion ofthe undesirable exhaust gas constituents emitted from an engine equippedwith an exhaust gas reaction device are emitted during this warmupperiod.

SUMMARY OF THE INVENTION This invention relates to internal-combustionengines equipped with exhaust gas reaction devices and is designed toprevent emission of undesirable exhaust gas constituents from enginesequipped with such reaction devices during starting of the engine andduring warmup of the reaction devices.

In particular, this invention collects exhaust gases or undesirableconstituents thereof passing unreacted through a reaction device whenthe temperature of the reaction device is below its efficient reactiontemperature and recirculates the collected exhaust gases or exhaust gasconstituents to the reaction device after its temperature reaches itseffiicient reaction level.

Several embodiments of this invention are set forth herein. It issuggested'that selected exhaust gas constituents formed while startingand during the warmup period be separated and stored in a container ofadsorptive, absorptive, or filtering material. As an alternative, it issuggested that the entire volume of exhaust gases formed while startingand during the warmup period be stored in an expansible container.

When thereaction device is warmed to an efficient reaction temperature,the stored exhaust gases or exhaust gas constituents are recycled to thereaction device and reacted therein. Thus undesirable exhaust gasconstituents are not emitted to the atmosphere while starting and duringthe warmup period.

The stored exhaust gases or exhaust gas constituents may be recycleddirectly to the reaction device. It is suggested that this beaccomplished by using a pump to draw the exhaust gases or exhaust gasconstituents from the storage container and deliver them to the reactiondevice; the pump also may deliver air to the reaction device to supportreaction of the exhaust gas constituents. As an alternative, it issuggested that the stored exhaust gases or exhaust gas constituents berecycled to the reaction device indirectly through the engine inductionsystem and combustion chambers, using the induction system vacuum todraw the exhaust gases or exhaust gas constituents from the storagecontainer.

THE PRIOR ART ments have not been limited to operation during the warmupperiod of an exhaust gas reaction device and have not ineluded anymechanism for purging and reacting constituents collected by theretention means. Thus such retention means would be quickly saturatedand rendered ineffective by the continuous flow of exhaust gasestherethrough.

In other proposals, exhaust gases would be retained in the reactiondevice until the reaction device became sufficiently warmed and theexhaust gas constituents reacted. With such an approach, however, thereaction device would require a large volume to store the exhaust gasesformed during the warmup period; the increased mass of this large volumewould require an even longer time to warm to an efficient reactiontemperature.

In addition, the prior art includes proposals to recirculate a portionof the exhaust gases through the engine combustion chamber. Theseproposals do not encompass the present invention because none suggeststhat the exhaust gases or constituents thereof be stored during warmupand subsequently recycled.

It will be appreciated, therefore, that this invention provides a noveland simple means for preventing emission to the atmosphere ofundesirable exhaust gas constituents and particularly those formed whenstarting and during initial operation of an engine.

The details as well as other objects and advantages of this inventionare shown in the drawings and are set forth in the description of thevarious embodiments.

SUMMARY OF THE DRAWINGS FIG. 1 -is a schematic view of one embodiment ofthis invention showing an internal-combustion engine having an exhaustgas reaction device in conjunction with an exhaust gas constituentcollection and recirculation system in which the exhaust gases passingunreacted through the reaction device are directed through a containerhaving filter, adsorption and absorption media which separateundesirable exhaust gas constituents from the exhaust gas flow. Thecontainer is connected to the engine induction system so that theseparated exhaust gas constituents are recycled through the combustionchambers as well as the exhaust gas reaction device.

FIG. 2 is a view of a portion of the embodiment of FIG. 1 showing thecontrol system when the reaction device is warmed to an efficientreaction temperature.

FIG. 3 is a schematic view of an alternative embodiment of thisinvention in which the container is connected to a pump which recyclesthe exhaust gas constituents directly to the reaction device through theexhaust manifold.

FIG. 4 is a view of a portion of the embodiment of FIG. 3 showing thecontrol system when the reaction device is warmed to an efficientreaction temperature.

FIG. 5 is a schematic view of another embodiment of this invention,similar to that of FIGS. 2 and 4, in which means are provided forheating airflow through the container to facilitate purging of theexhaust gas constituents from the storage media.

FIG. 6 is a schematic view of still another embodiment of this inventionin which the container expands to store the entire flow of exhaust gasesduring the warmup period.

FIG. 7 is a view of the embodiment of FIG. 6 showing the control systemwhen the reaction device is warmed to an efficient reaction temperature.

FIG. 8 is a schematic view of an embodiment of this invention whichcombines features of the embodiments of FIGS. 1 or 3 and 6.

FIG. 9 is a view of the embodiment of FIG. 8 showing the controlsystem-when the reaction device is warmed to an efficient reactiontemperature.

DESCRIPTION OF THE EMBODIMENTS Referring first to FIGS. 1 and 2, aninternal-combustion engine 10 has an'air cleaner 12, a carburetor 14including a throttle l6,.and anintake manifold 18 whichdefine an airinduction passage leading .to the engine combustion chambers.

Engine also has an exhaust passage defined by an exhaust manifold whichreceives gases exhausted from the combustion chambers, an exhaust pipe22, a catalytic converter 24, a diversion passage 26, and an outletpassage 28. As shown here, outlet passage 28 leads directly to theatmosphere; however, in some instances it may be desired to incorporateother exhaust gas reaction devices or silencing devices therein.

Converter 24 can efficiently promote reaction of undesirable exhaust gasconstituents under most conditions of operation, and emission of suchconstituents to the atmosphere is thereby prevented. However, converter24 must be heated to a minimum temperature to cause the necessaryreaction. Converter 24 is easily heated by the exhaust gases, but aperiod of about 1 to 3 minutes is usually required before the converterreaches the minimum temperature. Thus exhaust gases formed when startingthe engine and during initial operation are not efficiently reacted.

This invention therefore provides a valve 30, operated by a sensor 32which is responsive to the temperature of converter 24, to block theflow of exhaust gases through outlet passage 28 and to divert the flowof exhaust gases through diversion passage 26 to a container 34.

Container 34 includes a plurality of filter, adsorptive, and absorptivemedia for separating and storing undesirable exhaust gas constituents.These may include, for example, a filter medium 36 for separating andretaining particulates, an adsorptive medium 38 such as activatedcharcoal for separating and retaining hydrocarbons, an absorptivematerial 40 separating and retaining carbon monoxide, and an absorptivematerial 42 for separating and retaining oxides of nitrogen. Afterseparation of the undesirable exhaust gas constituents, the remainingexhaust gases flow out of container 34 through a fitting 44.

When converter 24 has been warmed to an efficient reaction temperature,sensor 32 moves valve to open outlet passage 28 and close diversionpassage 26. At the same time, a purge valve 46 is opened by sensor 32.Induction passage vacuum, transmitted through a purge line 48, theninduces an airflow through container 34 from fitting 44. A filter pad 50is provided to filter the air. In passing through the various filter,adsorption and absorption media 36, 38, 40 and 42, the air purgesexhaust gas constituents retained therein and delivers these unreactedconstituents through the engine induction passage and combustionchambers to converter 24. In passing through the combustion chambers andconverter 24, the undesirable constituents are reacted.

In this manner, this invention provides complete control of exhaustgases formed in engine 10. During most conditions of operation,converter 24 reacts the undesirable exhaust gas constituents andprevents emission thereof to the atmosphere. During the period requiredfor warmup of converter 24, the undesirable constituents are stored incontainer 34 for subsequent recycling through converter 24.

A metering orifice or purge control valve 52 may be included in purgeline 48 if desired.

Referring next to the embodiment of FIGS. 3 and 4, the exhaust gasconstituents may be recycled directly to the exhaust system instead ofindirectly through the induction system and the combustion chambers.Purge line 48 extends to the inlet of a pump 54 which also has a freshair inlet 56. The outlet 58 of pump 54 extends to a plurality ofinjection tubes 60 which discharge into exhaust manifold 20 adjacent thecombustion chamber exhaust ports. During the warmup period of converter24, purge valve 46 is closed and pump 54 delivers only fresh air toexhaust manifold 20. When converter 24 is warmed to an efficientreaction temperature, sensor 32 opens purge valve 46; pump 54 then drawsair through container 34 to purge unreacted exhaust gas constituentsfrom container 34. The unreacted exhaust gas constituents are mixed withthe stream of air delivered by pump 54 to the exhaust system and reactedin converter 24.

It will be appreciated that the metering orifice or purge control valve52 shown in the embodiment of FIGS. 1 and 2 may also be included in theembodiment of FIGS. 3 and 4. It also will be appreciated that othermeans may be utilized to purge the exhaust gas constituents fromcontainer 34 and recycle these constituents to converter 24.

It may be desirable to heat the adsorption and absorption media incontainer 34 to facilitate purging of the exhaust gas constituentsretained therein. Referring to the embodiment of FIG. 5, this may beaccomplished by passing the purge air through a heat exchanger 62disposed about exhaust passage 28. In passing through heat exchanger 62,the air will be heated by the exhaust gases flowing from converter 24;the heated air will in turn heat the various media within container 34.In the FIG. 5 embodiment, it will be appreciated that purge passage 48may include the metering orifice or purge control valve 52 shown in FIG.1 and may extend either to the induction passage as shown in FIG. 1 orto pump 54 as shown in FIG. 3. It also will be appreciated that othermeans are available to heat container 34 in place of heat exchanger 62.

Referring next to the embodiment of FIGS. 6 and 7, diversion passage 26directs unreacted exhaust gases from converter 24 to a container 64providing an expansible chamber 66. During the warmup period, the entireflow of exhaust gases is collected in chamber 66. When reactor 24 isfully warmed, sensor 32 opens valve 46 and exhaust gases stored inchamber 66 are drawn through purge line 48 either to the inductionpassage as shown in FIGS. 1 and 2 or to pump 54 as shown in FIGS. 3 and4. The unreacted exhaust gases are thereby recycled for reaction inconverter 24. It will be appreciated that, here too, purge line 48 mayinclude the metering orifice or purge control valve 52 shown in FIG. 1.

FIGS. 8 and 9 show one of several possible embodiments using containers34 and 64 in combination. Referring to FIG. 8, valve 30 diverts the flowof exhaust gases through diversion passage 26 into expansible container64 during the time in which converter 24 is being heated. An overflowpassage 68 extends from container 64 to container 34. Passage 68 maycontain suitable pressure control valves if desired. Thus if thecapacity of chamber 66 is exceeded, the excess exhaust gases travelthrough passage 68 to container 34 where the undesirable exhaust gasconstituents are separated and retained.

As shown in FIG. 9, after converter 24 is warmed to an efficientreaction temperature, sensor 32 moves valve 30 to close diversionpassage 26 and open outlet passage 28. At the same time, a valve 46a isopened; fresh air then is drawn into container 34 through fitting 44,and the unreacted exhaust gas constituents are purged through a line 48aand line 48. In addition, a valve 46b is moved to close overflow passage68 and to open a purge line 4812; the exhaust gases stored in expansiblechamber 66 are then purged through line 48b and 48. Here again, it willbe appreciated that purge line 48 may extend either to the engineinduction system as shown in FIG. 1 or to pump 54 as shown in FIG. 3 andmay include the metering orifice or purge control valve 52 as shown inFIG. 1. Moreover, fitting 44 may extend to the heat exchanger 62 asshown in FIG. 5.

It will be appreciated that the warmup characteristics of other exhaustgas reaction devices, such as a thermal reactor incorporated in theexhaust manifold, display similar delays in reaching an efficientreaction temperature. It is contemplated that this invention would beequally advantageous when used with such devices.

The two embodiments 34 and 64 of the storage container have individualadvantages. Container 34 with its various filter, adsorption, andabsorption media selectively separates and retains certain of theexhaust gas constituents. Charcoal 38, for example, is known for itsefficiency in separating and retaining hydrocarbons and is particularlyeffective in retaining the high molecular weight hydrocarbons which havebeen alleged to be carcinogenic. Expansible container 64, on the otherhand, collects all exhaust gases formed during starting and wannup.

In testing this invention, container 34 was provided with about 5gallons, 45 pounds, of activated charcoal. The amount required in actualuse will vary with the time required for converter 24 to reach anefficient reaction temperature and with the volume of exhaust gasesproduced by engine during that time. This invention also was tested byforming container 64 from a bag having a volume of 75 cubic feet and bydischarging exhaust gases thereto at atmospheric pressure. The volumerequired for container 64 in actual use would vary with the timerequired for converter 24 to reach an efficient reaction temperature andwith the volume of exhaust gases produced by engine 10 during this time.The volume required for container 64 may be reduced if exhaust gases arestored at pressures higher than atmospheric. In such circumstances,container 64 may require a pressure relief valve.

It is anticipated that the effectiveness of container 34 to separate andstore exhaust gas constituents will not diminish substantially evenafter a large number of charging and stripping cycles. The separationand retention efficiency of container 34 may be measured by flowing testgases through one end and sampling outflow through the opposite end.

Although converter 24 is shown here as displaced somewhat from manifold20, it will be appreciated that the efficiency of a catalytic converteris generally enhanced and the warmup time reduced when it is disposedclose to manifold 20.

From the foregoing, it will be appreciated that this invention providesa two phase mechanism for controlling exhaust gas emissions. As theengine is started and during initial operation, undesirable exhaust gasconstituents are collected in a storage container. After the warmupperiod, an exhaust gas reaction device is utilized to prevent emissionof undesirable constituents and the unreacted constituents formed duringstarting,and warmup are recycled through the reaction device.

We claim:

1. The method of purifying gases exhausted from a combustion chambercomprising the steps of:

passing the gases through an exhaust gas reaction device effective tocause reaction of exhaust gas constituents when the temperature of saidreaction device is above a minimum temperature,

collecting and retaining in a storage container exhaust gas constituentspassed unreacted through said reaction device when the temperature ofsaid reaction device is below said minimum temperature,

and recycling the retained exhaust gas constituents from said storagecontainer through said reaction device when the temperature of saidreaction device is above said minimum temperature, whereby exhaust gasconstituents passed unreacted through said reaction device when thetemperature of said reaction device is below said minimum temperatureare recycled through and reacted in said reaction device when thetemperature of said reaction device is above said minimum temperature.2. The method of operation an internal-combustion engine having acombustion chamber, an exhaust passage for exhaust gas flow from saidcombustion chamber to the atmosphere, and an exhaust gas reaction devicein said exhaust passage effective to cause reaction of exhaust gasconstituents flowing therethrough when the temperature of said reactiondevice is above a minimum temperature to thereby prevent emission ofsuch constituents to the atmosphere, said method comprising the stepsof:

blocking said exhaust passage downstream of said reaction device whenthe temperature of said reaction device is below said minimumtemperature to thereby prevent emission of unreacted exhaust gasconstituents to the atmosphere, directing exhaust gases flowingunreacted from said reaction device when the temperature of saidreaction device is below said minimum temperature to a storage meanseffective to retain unreacted exhaust gas constituents,

permitting exhaust gases to flow through said exhaust passage from saidreaction device to the atmosphere when the temperature of said reactiondevice is above said minimum temperature, said reaction device thenbeing effective to cause reaction of exhaust gas constituents to therebyprevent emission of such constituents to the atmosphere,

and recycling the retained exhaust gas constituents from said storagemeans to said reaction device when the temperature of said reactiondevice is above said minimum temperature whereby said reaction devicecauses reaction of retained exhaust gas constituents and whereby saidstorage means is purged or unreacted exhaust gas constituents and isprepared for future retention of further unreacted exhaust gasconstituents.

3. In an internal-combustion engine power plant having a combustionchamber, an exhaust passage for exhaust gas flow from said combustionchamber to the atmosphere, and an ex haust gas reaction device in saidexhaust passage effective to cause reaction of exhaust gas constituentsflowing therethrough when the temperature of said reaction device isabove a minimum temperature to thereby prevent emission of suchconstituents to the atmosphere, the combination comprising:

storage means for retaining unreacted exhaust gas constituents,

means for preventing exhaust gases flowing unreacted through saidreaction device when the temperature of said reaction device is belowsaid minimum temperature from flowing to the atmosphere and fordirecting such exhaust gases into said storage means whereby unreactedexhaust gas constituents are retained in said storage means,

and means for recycling the retained exhaust gas constituents from saidstorage means to said reaction device when the temperature of saiddevice is above said minimum temperature, whereby exhaust gasconstituents flowing unreacted through said reaction device when thetemperature of said reaction device is below said minimum temperatureare recycled through and reacted in said reaction device when thetemperature of said reaction device is above said minimum temperature.4. The combination set forth in claim 3 wherein said storage meanscomprises a container which expands as exhaust gases are directedthereto and which contracts as exhaust gases are recycled therefrom.

5. The combination set forth in claim 3 wherein said storage meanscomprises material which separates certain exhaust gas constituents fromthe flow of exhaust gases directed thereto.

6. The combination set forth in claim 5 wherein said material includesactivated charcoal which adsorbs hydrocarbons from the flow of exhaustgases directed thereto.

7. In an internal-combustion engine power plant having a combustionchamber, an exhaust passage for exhaust gas flow from said combustionchamber to the atmosphere, an exhaust gas reaction device in saidexhaust passage effective to cause reaction of exhaust gas constituentsflowing therethrough when the temperature of said reaction device isabove a minimum temperature to thereby prevent emission of suchconstituents to the atmosphere, and means for delivering air to saidreaction device to support reaction of exhaust gas constituents therein,the combination comprising:

storage means for retaining unreacted exhaust gas constituents, meansfor preventing exhaust gases flowing unreacted through said reactiondevice when the temperature of said reaction device is below saidminimum temperature from flowing to the atmosphere and for directingsuch exhaust gases into said storage means whereby unreacted exhaust gasconstituents are retained in said storage means,

and means for directing the retained exhaust gas constituents from saidstorage means to said air delivering means when the temperature of saidreaction device is above said minimum temperature to thereby recycleunreacted exhaust gas constituents to said reaction device,

whereby exhaust gas constituents flowing unreacted through said reactiondevice when the temperature of said reaction device is below saidminimum temperature are recycled through and reacted in said reactiondevice when the temperature of said reaction device is above saidminimum temperature. emission 8. In an intemal-combustion engine powerplant having a combustion chamber, an induction passage for airflow tosaid combustion chamber, an exhaust passage for exhaust gas flow fromsaid combustion chamber to the atmosphere, and an exhaust gas reactiondevice in said exhaust passage effective to cause reaction of exhaustgas constituents flowing therethrough when the temperature of saidreaction device is above a minimum temperature to thereby preventemission of such constituents to the atmosphere, the combinationcomprising:

storage means for retaining unreacted exhaust gas constituents,

means for preventing exhaust gases flowing unreacted through saidreaction device when the temperature of said reaction device is belowsaid minimum temperature from flowing to the atmosphere and fordirecting such exhaust gases into said storage means whereby unreactedexhaust gas constituents are retained in said storage means,

and means for directing the retained exhaust gas constituents from saidstorage means to said induction passage when the temperature of saidreaction device is above said minimum temperature to thereby recycleunreacted exhaust gas constituents to said combustion chamber and saidreaction device,

whereby exhaust gas constituents flowing unreacted through said reactiondevice when the temperature of said reaction device is below saidminimum temperature are recycled through and reacted in said reactiondevice when the temperature of said reaction device is above saidminimum temperature.

9. In an intemal-combustion engine having-a combustion chamber whichexhausts gases through an exhaust gas reaction device effective to causereaction of exhaust gas constituents when the temperature of saidreaction device is above a minimum temperature, the combinationcomprising:

means for separating and storing certain unreacted exhaust gasconstituents from a flow of exhaust gases, means for directing theexhaust gases flowing unreacted from said reaction device when thetemperature of said reaction device is below said minimum temperaturethrough said separating and storing means whereby unreacted exhaust gasconstituents are separated and stored therein, and means for directingair through said separating and storing means and into said reactiondevice when the temperature of said reaction device is above saidminimum temperature to thereby strip the unreacted exhaust gasconstituents from said separating and storing means and recycle suchconstituents to said reaction device,

whereby exhaust gas constituents flowing unreacted through said reactiondevice when the temperature of said reaction device is below saidminimum temperature are recycled through and reacted in said reactiondevice when the temperature of said reaction device is above saidminimum temperature.

10. The combination set forth in claim 9 which further comprises meansfor applying heat to said separating and storing means when thetemperature of said reaction device is above said minimum temperature tothereby promote stripping of unreacted exhaust gas constituents fromsaid separating and storing means.

11. The combination set forth in claim 10 wherein said heat applyingmeans heats the air directed through said separating and storing means.

12. In an internal-combustion engine power plant having a combustionchamber, an outlet passage opening to the atmosphere, an exhaust gasreaction device disposed between said combustion chamber and said outletpassage and effective to cause reaction of exhaust gas constituentsflowing therethrough from said combustion chamber to said outlet passagewhen the temperature of said reaction device is above a minimumtemperature to thereby prevent emission of such constituents to theatmosphere, the combination comprising:

storage means for retaining unreacted exhaust gas constituents, adiversion passage connecting said storage means and said reactiondevice, means for sensing the temperature of said reaction device, valvemeans disposed in said outlet and diversion passages and operated bysaid temperature sensing means for closing said outlet passage andopening said diversion passage when the temperature of said reactiondevice is below said minimum temperature to direct unreacted exhaust gasconstituents into said storage means and prevent emission of suchconstituents to the atmosphere, said valve means being further operatedby said temperature sensing means for opening said outlet passage andclosing said diversion passage when the temperature of said reactiondevice is above said minimum temperature, and means for recyclingretained exhaust gas constituents from said storage means to saidreaction device when the temperature of said reaction device is abovesaid minimum temperature, whereby exhaust gas constituents flowingunreacted through said reaction device when the temperature of saidreaction device is below said minimum temperature are recycled throughand reacted in said reaction device when the temperature of saidreaction device is above said minimum temperature. 13. In aninternal-combustion engine having a combustion chamber, the combinationcomprising:

an exhaust gas reaction device having an inlet passage connected to saidcombustion chamber for receiving gases exhausted therefrom and havingfirst and second discharge passages, said reaction device beingeflective to cause reaction of exhaust gas constituents when thetemperature of said reaction device is above a minimum temperature,storage means for retaining unreacted exhaust gas constituents, saidfirst discharge passage opening directly to atmosphere, said seconddischarge passage extending to said storage means, valve means in saiddischarge passages for closing said first discharge passage whileopening said second discharge passage and for opening said firstdischarge passage while closing said second discharge passage, meansresponsive to the temperature of said reaction device for causing saidvalve means to close said first discharge passage and open said seconddischarge passage when the temperature of said reaction device is belowsaid minimum temperature whereby flow of unreacted exhaust gasconstituents to the atmosphere is prevented and unreacted exhaust gasconstituents are retained in said storage means, said temperatureresponsive means also being responsive to the temperature of saidreaction device for causing said valve means to open said firstdischarge passage and close said second discharge passage when thetemperature of said reaction device is above said minimum temperature, areturn passage connecting said storage means to said inlet passage forrecycling the retained exhaust gas constituents from said storage meansto said reaction device, and additional valve means in said returnpassage, said temperature responsive means further being responsive tothe temperature of said reaction device for causing said additionalvalve means to close said return passage when the temperature of saidreaction device is below said minimum temperature and to open saidreturn passage when the temperature of said reaction device is abovesaid minimum temperature,

whereby exhaust gas constituents flowing unreacted through said reactiondevice when the temperature of said reaction device is below saidminimum temperature are recycled through and reacted in said reactiondevice when the temperature of said reaction device is above saidminimum temperature.

14. The combination set forth in claim 13 wherein said storage meansincludes a first container which expands as ex-- haust gases aredirected thereto and contracts as exhaust gases are recycled therefrom,a second container of material which separates certain unreacted exhaustgas constituents from the

1. The method of purifying gases exhausted from a combustion chambercomprising the steps of: passing the gases through an exhaust gasreaction device effective to cause reaction of exhaust gas constituentswhen the temperature of said reaction device is above a minimumtemperature, collecting and retaining in a storage container exhaust gasconstituents passed unreacted through said reaction device when thetemperature of said reaction device is below said minimum temperature,and recycling the retAined exhaust gas constituents from said storagecontainer through said reaction device when the temperature of saidreaction device is above said minimum temperature, whereby exhaust gasconstituents passed unreacted through said reaction device when thetemperature of said reaction device is below said minimum temperatureare recycled through and reacted in said reaction device when thetemperature of said reaction device is above said minimum temperature.2. The method of operation an internal-combustion engine having acombustion chamber, an exhaust passage for exhaust gas flow from saidcombustion chamber to the atmosphere, and an exhaust gas reaction devicein said exhaust passage effective to cause reaction of exhaust gasconstituents flowing therethrough when the temperature of said reactiondevice is above a minimum temperature to thereby prevent emission ofsuch constituents to the atmosphere, said method comprising the stepsof: blocking said exhaust passage downstream of said reaction devicewhen the temperature of said reaction device is below said minimumtemperature to thereby prevent emission of unreacted exhaust gasconstituents to the atmosphere, directing exhaust gases flowingunreacted from said reaction device when the temperature of saidreaction device is below said minimum temperature to a storage meanseffective to retain unreacted exhaust gas constituents, permittingexhaust gases to flow through said exhaust passage from said reactiondevice to the atmosphere when the temperature of said reaction device isabove said minimum temperature, said reaction device then beingeffective to cause reaction of exhaust gas constituents to therebyprevent emission of such constituents to the atmosphere, and recyclingthe retained exhaust gas constituents from said storage means to saidreaction device when the temperature of said reaction device is abovesaid minimum temperature whereby said reaction device causes reaction ofretained exhaust gas constituents and whereby said storage means ispurged or unreacted exhaust gas constituents and is prepared for futureretention of further unreacted exhaust gas constituents.
 3. In aninternal-combustion engine power plant having a combustion chamber, anexhaust passage for exhaust gas flow from said combustion chamber to theatmosphere, and an exhaust gas reaction device in said exhaust passageeffective to cause reaction of exhaust gas constituents flowingtherethrough when the temperature of said reaction device is above aminimum temperature to thereby prevent emission of such constituents tothe atmosphere, the combination comprising: storage means for retainingunreacted exhaust gas constituents, means for preventing exhaust gasesflowing unreacted through said reaction device when the temperature ofsaid reaction device is below said minimum temperature from flowing tothe atmosphere and for directing such exhaust gases into said storagemeans whereby unreacted exhaust gas constituents are retained in saidstorage means, and means for recycling the retained exhaust gasconstituents from said storage means to said reaction device when thetemperature of said device is above said minimum temperature, wherebyexhaust gas constituents flowing unreacted through said reaction devicewhen the temperature of said reaction device is below said minimumtemperature are recycled through and reacted in said reaction devicewhen the temperature of said reaction device is above said minimumtemperature.
 4. The combination set forth in claim 3 wherein saidstorage means comprises a container which expands as exhaust gases aredirected thereto and which contracts as exhaust gases are recycledtherefrom.
 5. The combination set forth in claim 3 wherein said storagemeans comprises material which separates certain exhaust gasconstituents from the flow of exhaust gases directed thereto.
 6. Thecombination set forth in claim 5 wherein said material incluDesactivated charcoal which adsorbs hydrocarbons from the flow of exhaustgases directed thereto.
 7. In an internal-combustion engine power planthaving a combustion chamber, an exhaust passage for exhaust gas flowfrom said combustion chamber to the atmosphere, an exhaust gas reactiondevice in said exhaust passage effective to cause reaction of exhaustgas constituents flowing therethrough when the temperature of saidreaction device is above a minimum temperature to thereby preventemission of such constituents to the atmosphere, and means fordelivering air to said reaction device to support reaction of exhaustgas constituents therein, the combination comprising: storage means forretaining unreacted exhaust gas constituents, means for preventingexhaust gases flowing unreacted through said reaction device when thetemperature of said reaction device is below said minimum temperaturefrom flowing to the atmosphere and for directing such exhaust gases intosaid storage means whereby unreacted exhaust gas constituents areretained in said storage means, and means for directing the retainedexhaust gas constituents from said storage means to said air deliveringmeans when the temperature of said reaction device is above said minimumtemperature to thereby recycle unreacted exhaust gas constituents tosaid reaction device, whereby exhaust gas constituents flowing unreactedthrough said reaction device when the temperature of said reactiondevice is below said minimum temperature are recycled through andreacted in said reaction device when the temperature of said reactiondevice is above said minimum temperature. emission
 8. In aninternal-combustion engine power plant having a combustion chamber, aninduction passage for airflow to said combustion chamber, an exhaustpassage for exhaust gas flow from said combustion chamber to theatmosphere, and an exhaust gas reaction device in said exhaust passageeffective to cause reaction of exhaust gas constituents flowingtherethrough when the temperature of said reaction device is above aminimum temperature to thereby prevent emission of such constituents tothe atmosphere, the combination comprising: storage means for retainingunreacted exhaust gas constituents, means for preventing exhaust gasesflowing unreacted through said reaction device when the temperature ofsaid reaction device is below said minimum temperature from flowing tothe atmosphere and for directing such exhaust gases into said storagemeans whereby unreacted exhaust gas constituents are retained in saidstorage means, and means for directing the retained exhaust gasconstituents from said storage means to said induction passage when thetemperature of said reaction device is above said minimum temperature tothereby recycle unreacted exhaust gas constituents to said combustionchamber and said reaction device, whereby exhaust gas constituentsflowing unreacted through said reaction device when the temperature ofsaid reaction device is below said minimum temperature are recycledthrough and reacted in said reaction device when the temperature of saidreaction device is above said minimum temperature.
 9. In aninternal-combustion engine having a combustion chamber which exhaustsgases through an exhaust gas reaction device effective to cause reactionof exhaust gas constituents when the temperature of said reaction deviceis above a minimum temperature, the combination comprising: means forseparating and storing certain unreacted exhaust gas constituents from aflow of exhaust gases, means for directing the exhaust gases flowingunreacted from said reaction device when the temperature of saidreaction device is below said minimum temperature through saidseparating and storing means whereby unreacted exhaust gas constituentsare separated and stored therein, and means for directing air throughsaid separating and storing means and into said reaction device when thetemperature of Said reaction device is above said minimum temperature tothereby strip the unreacted exhaust gas constituents from saidseparating and storing means and recycle such constituents to saidreaction device, whereby exhaust gas constituents flowing unreactedthrough said reaction device when the temperature of said reactiondevice is below said minimum temperature are recycled through andreacted in said reaction device when the temperature of said reactiondevice is above said minimum temperature.
 10. The combination set forthin claim 9 which further comprises means for applying heat to saidseparating and storing means when the temperature of said reactiondevice is above said minimum temperature to thereby promote stripping ofunreacted exhaust gas constituents from said separating and storingmeans.
 11. The combination set forth in claim 10 wherein said heatapplying means heats the air directed through said separating andstoring means.
 12. In an internal-combustion engine power plant having acombustion chamber, an outlet passage opening to the atmosphere, anexhaust gas reaction device disposed between said combustion chamber andsaid outlet passage and effective to cause reaction of exhaust gasconstituents flowing therethrough from said combustion chamber to saidoutlet passage when the temperature of said reaction device is above aminimum temperature to thereby prevent emission of such constituents tothe atmosphere, the combination comprising: storage means for retainingunreacted exhaust gas constituents, a diversion passage connecting saidstorage means and said reaction device, means for sensing thetemperature of said reaction device, valve means disposed in said outletand diversion passages and operated by said temperature sensing meansfor closing said outlet passage and opening said diversion passage whenthe temperature of said reaction device is below said minimumtemperature to direct unreacted exhaust gas constituents into saidstorage means and prevent emission of such constituents to theatmosphere, said valve means being further operated by said temperaturesensing means for opening said outlet passage and closing said diversionpassage when the temperature of said reaction device is above saidminimum temperature, and means for recycling retained exhaust gasconstituents from said storage means to said reaction device when thetemperature of said reaction device is above said minimum temperature,whereby exhaust gas constituents flowing unreacted through said reactiondevice when the temperature of said reaction device is below saidminimum temperature are recycled through and reacted in said reactiondevice when the temperature of said reaction device is above saidminimum temperature.
 13. In an internal-combustion engine having acombustion chamber, the combination comprising: an exhaust gas reactiondevice having an inlet passage connected to said combustion chamber forreceiving gases exhausted therefrom and having first and seconddischarge passages, said reaction device being effective to causereaction of exhaust gas constituents when the temperature of saidreaction device is above a minimum temperature, storage means forretaining unreacted exhaust gas constituents, said first dischargepassage opening directly to atmosphere, said second discharge passageextending to said storage means, valve means in said discharge passagesfor closing said first discharge passage while opening said seconddischarge passage and for opening said first discharge passage whileclosing said second discharge passage, means responsive to thetemperature of said reaction device for causing said valve means toclose said first discharge passage and open said second dischargepassage when the temperature of said reaction device is below saidminimum temperature whereby flow of unreacted exhaust gas constituentsto the atmosphere is prevented and unreacted exhaust gas Constituentsare retained in said storage means, said temperature responsive meansalso being responsive to the temperature of said reaction device forcausing said valve means to open said first discharge passage and closesaid second discharge passage when the temperature of said reactiondevice is above said minimum temperature, a return passage connectingsaid storage means to said inlet passage for recycling the retainedexhaust gas constituents from said storage means to said reactiondevice, and additional valve means in said return passage, saidtemperature responsive means further being responsive to the temperatureof said reaction device for causing said additional valve means to closesaid return passage when the temperature of said reaction device isbelow said minimum temperature and to open said return passage when thetemperature of said reaction device is above said minimum temperature,whereby exhaust gas constituents flowing unreacted through said reactiondevice when the temperature of said reaction device is below saidminimum temperature are recycled through and reacted in said reactiondevice when the temperature of said reaction device is above saidminimum temperature.
 14. The combination set forth in claim 13 whereinsaid storage means includes a first container which expands as exhaustgases are directed thereto and contracts as exhaust gases are recycledtherefrom, a second container of material which separates certainunreacted exhaust gas constituents from the flow of exhaust gasesdirected thereto, and an overflow passage extending from said firstcontainer to said second container, and wherein said second dischargepassage extends to said first container, whereby at least a portion ofthe entire exhaust gas flow is retained in said first container andwhereby certain unreacted exhaust gas constituents are separated fromany remaining portion of the exhaust gas flow through said seconddischarge passage and are retained in said second container.